A dual mode microstrip antenna element has been investigated which has two independently excitable modes resonant at the same frequency. This element has been shown to be capable of producing a broadside maximum, a broadside null, or an end-fire type pattern by suitable choice of its reactive loads and suitable excitation of its degenerate modes. Appropriately located loads can be used to resonate modes normally resonant at quite different frequencies, at a single, common frequency. The results indicate that the nodal lines of the loaded element are accurately predicted by the generalized theory of loaded microstrip antennas, and that two modes can be excited independently of each other by feeding each mode along the nodal line of the other. To verify the theoretical predictions an actual dual mode microstrip element was fabricated and tested. The results of this experiment correlate well with the theoretical model with respect to the overall characteristics of the radiator.

The advent of the D-1 cassette standard will have a profound impact upon the instrumentation tape recording industry starting in about 1990. Under the auspices of the Society of Motion Picture and Television Engineers (SMPTE) and the European Broadcast Union (EBU), broadcasters, media manufacturers and television recorder manufacturers have developed a series of standards governing digital recording of television signals using a set of standard, high-quality cassettes. To support television applications, two specific formats are necessary to cover the marketplace; a “component” format, which is independent of the television standard and compatible with a digital studio, and a “composite” format which is dependent upon the national format and is compatible with analog studios found today. Standards are in place covering 4:2:2 digital component recording. Proposals covering composite digital recording formats are now being discussed in the industry. As the only U.S. recorder manufacturer with a declared intent to manufacture hardware for the television industry to these standards, Ampex has participated in the generation of these standards. This paper will discuss the cassette and data standards which have been created for the television industry. Where deficiencies and limitations in those standards exist for data recording, these will be pointed out.

The Advanced Range Instrumentation Aircraft (ARIA) is an airborne platform to receive, record, process and retransmit telemetry data. This paper presents a summary of ARIA’s capabilities with emphasis on airborne testing of the Advanced Medium Range Air to Air Missile (AMRAAM) program. The unique test scenarios, as well as current and future telemetry requirements of the AMRAAM test program are discussed.

The Airborne Platform Telemetry Relay System (AP/TM) is currently being built for the Gulf Range Instrumentation System. The AP/TM will allow air-to-air missile test and training missions to be conducted beyond the line-of-sight of land-based instrumentation. The AP/TM is comprised of the following subsystems: C a Telemetry Data Relay C a Sea Surveillance Radar and Radar Data Link C a Drone Control Relay C a UHF Radio Relay The Telemetry Data Relay Subsystem will receive telemetry signals from five independent sources and will retransmit them to land based receiving sites. This subsystem contains a 75 square foot, electronically steerable, five beam phased array antenna and uses polarization diversity to eliminate polarization mismatch loss and to improve reception in the presence of multipath propagation. The AP/TM will also have the capability of relaying four channels of voice communications and drone tracking data and to perform sea surveillance of the mission area. The coordinates of targets detected by the radar will be relayed to the range control center over a high frequency (HF) data link. In addition to the airborne equipment, the system also includes a ground support instrumentation van which is used for pre- and post-flight checkout and maintenance.

A simple adaptive algorithm is employed in the determination of operating parameters for a sequential probability ratio test (SPRT) type of PCM frame synchronizer. Performance data over a wide range of bit error rates are obtained by computer simulation. These data show a significant improvement in lock-to-search transition performance of the SPRT over the so-called conventional type of synchronizer.

With the advent of higher and higher data rates and signal processing requirements for onboard satellite processing, the need for a faster computational capability has grown well beyond the capabilities of existing space-qualified computers. This has become a major technical issue in the design of next-generation satellite systems for commercial and military use. As a matter of fact, it is becoming a major issue in the Strategic Defense Initiative (SDI), the development of the MILSTAR Satellite System, and in future infrared (IR) and radar satellites/platforms. Future platforms will require larger onboard processing systems than are currently in use in order to satisfy their data processing and commandand-control communications requirements. The platforms of tomorrow will be very sophisticated and therefore expensive. For such systems to have acceptable life-cycle costs, they must be produced from highly reliable hardware that will operate in space for system design lifetimes of up to 10 years. This paper will summarize the processing needs of onboard systems and present a specific example of the design of a VLSI/VHSIC processor for an onboard satellite controller in an airborne platform.

Availability of low cost microcomputers, LSI devices have made it necessary to recast the architecture of aerospace telemetry system to realize all the attendant benefits. System constraints and the resultant hardware design are described in this paper.

Modernizing labor intensive Remote Tracking Stations (RTS), increasing individual station capacity, and providing interoperable links between three separate Air Force satellite networks are the objectives of the Automated RTS (ARTS) program now half way to completion.

Today I will describe the application of the Autocorrelation function to the Magnetic Recording Channel. I will explain what is an autocorrelated function, how does it behave and where may it be applied in the Magnetic Recording channel. There will be a brief description of Kodak San Diego’s Autocorrelator and how we apply this technology. If I have done my job well at the end of this presentation you will have enough knowledge about autocorrelation to access your own application. Before I start, let me give a brief overview on the application of an Autocorrelator. The Autocorrelator can be used to collect information on signals in a magnetic recording system and display this information graphically as a statistical plot. Autocorrelation, in the time domain, is the counter part to a spectrum analyzer in the frequency domain (Fourier Pair). The information about the signal of interest must be stored for post analysis. This information called a database must then be processed by a computer. The computer passes the database through the autocorrelation algorithm and produces a second database. This second database represents a plot of the autocorrelated function. The next step is to plot the database on a video screen. This plot can be examined for periodicities, randomness, and relational influences on a captured signal. In our application, this signal is an error flag or a dropout flag. We want a statistical picture of the magnitude of errors and their relative frequency. The information gained from Autocorrelation can aid in solutions for: Error Correction Codes Media Evaluation/Qualifications Media Process Defect Identification Mechanical Eccentricities Modulation Code Performances System’s Figure of Merit To use a cliche, “one picture is worth a thousand words,” is exactly the point of the Autocorrelator’s graphical display. It yields information useful to those disciplines which often find difficulty in describing an event in understandable terms.

This paper presents a method developed to automate the data base entry and setup of the ADS 100 Decommutation System. Automation was accomplished by interfacing an existing RS-232C port with a VAX computer. Other available interface options are considered. The automated system provides a method for rapid data entry while minimizing errors. Automation also eliminates the continuing requirement for a skilled ADS 100 programmer. Additional topics reviewed are the various problems encountered while developing the interface. Also discussed is the development and interface of host computer software, including the predefined ADS 100 record structures. The final result is a complete and accurate digital data base setup in the ADS 100 system.

This paper describes a microprocessor based multi-channel signal analyzer system for use with telemetry system pre- and post detected video signals. In the application described here, the system software is configured to simultaneously analyze up to 16 telemetry signals, compute an estimate of the SNR for each, and then select the best for output to real time recording equipment. The SNR is estimated by comparing the total signal energy with the signal power observed in an unused portion of the signal spectrum. The signal analysis filters are fully programmable over a range of 10 KHz to 2 MHz and may be set up to analyze a wide variety of telemetry formats. The microprocessor system also supports printed output of signal status and remote programming.

The National Bureau of Standards (NBS) has investigated the calibration and measurement support requirements of millimeter wave satellite systems such as MILSTAR. Essentially three new measurement problems arise because of operating in the upper SHF and EHF frequency ranges. First, without adequate methods to measure the atmospheric loss, the accuracy of EIRP measurements in the 20 GHz to 45 GHz range can be no better than 0.5 dB to 3 dB (depending on frequency and antenna elevation angle). The atmosphere absorbs and scatters radiation traveling through it, both reducing the magnitude of and depolarizing a received signal. Second, standards, measurement support services, and some measurement techniques are not presently available from NBS and they are needed to support millimeter wave antenna gain and thermal noise measurements. Of special concern are the effects of connectors and adapters, since they can introduce significant errors into mm-wave measurements. Theird, if the sun and/or moon are to be used for measuring earth terminal G/T, earth terminal antenna gain, or satellite effective isotropic radiated power in the millimeter region, they need to be appropriately characterized at those frequencies. The sun and moon are only useful as measurement sources for antenna systems with gains less than about 50 dB, but most MILSTAR systems are expected to fall in this category.

Description of various off-line magnetic tape cleaning techniques and testing process to measure defects of tape before using it for tape recording applications. Discussions are made on the type of cleaning methods and also the ways and means to achieve better evaluation results.

Spread Spectrum Systems have the potential of sharing the frequency spectrum with broadcasting, telephony and data communications services due to their low power density signalling. The study of feasibility of co-existence of Direct Sequence Spread Spectrum ranging signal with TV or SCPC carriers in a common satellite transponder is presented in this paper. The suitability of this type of ranging for Indian National Satellite-IB (INSAT-IB) system from Master Control Facility (MCF), Hassan, India has been examined. The mutual interference effects between spread spectrum ranging signal and TV or SCPC services through various sizes of earth stations in INSAT network have been calculated. The study indicates that simultaneous accurate range measurement by spread spectrum technique from control earth station is possible without any significant degradation in signal quality of TV or SCPC services.

The Air Force Satellite Control Network (AFSCN) provides real-time telemetry, tracking and command (TT&C) services for the Department of Defense (DoD) space systems. It consists of a worldwide network of Remote Tracking Stations (RTSs), the Air Force Satellite Test Center (STC), at Sunnyvale, California, and the soon to be completed Consolidated Space Operations Center (CSOC), located near Colorado Springs, Colorado. The object of this paper is to present an overview of the wideband communications systems which provide connectivity between these elements, and the planned evolution of the communications architecture required to support future growth.

A major factor in the performance of a Telemetry System over the sea is the effect of multipath. The reflected signal from the surface of the sea may, in general, add to or subtract from the direct signal, and may therefore lead to severe fading and possible loss of useful signal. The multipath is a function of the sea state and the polarization of the signal. In order to reduce the effect of multipath on performance, a dual polarization diversity system is being built for the Airborne Telemetry Relay System for the Gulf Range. An analysis of the performance of the dual polarization diversity system in the presence of multipath for different sea states, different reflection angles, and different initial polarization angles is presented. For comparison, a similar analysis is presented for a circular polarization receiving antenna system.

The TI 4100 Geodetic Global Positioning System (GPS) Receiver has been field tested in several environments. These include collocation rooftop tests near reflective equipment, isolated desert positioning tests, and shipboard survey tests. The receiver data consisted of pseudorange (code) and biased Doppler range (phase) measurements on both L1 and L2 frequency channels. This paper compares differences between ionospherically corrected pseudorange and biased Doppler range measurements to demonstrate the significant effects of signal multipath on the pseudorange measurements. That is, pseudorange signal multipath effects can be isolated, detected, and statistically modeled using only the above measurements. Examples are given for various receiver antenna locations. Day-to-day comparisons are made to demonstrate the repeated multipath effects due to repeated satellite-to-antenna geometries. The results can be used to analyze and statistically model pseudorange multipath effects for possible improved positioning and GPS satellite orbit determination accuracy.

The success of a communications satellite mission depends not only on the proper operation of the on-board Attitude and Orbit Control System (AOCS), but also on the complex interaction between the spacecraft and the ground control center. In support of a satellite program from its inception to launch and throughout the inorbit life, COMSAT has developed a SATELLITE ATTITUDE AND ORBIT CONTROL SYSTEM FLIGHT SIMULATOR. This paper describes the design and operations of the COMSAT FLIGHT SIMULATOR. The simulator is a real-time, high fidelity, operator interactive, spacecraft hardware in the loop system. The heart of the system is a high precision minicomputer in which the spacecraft dynamics, sensors, actuators and most likely failure modes are modeled. A significant feature of the simulator is a faithful duplication of the command and telemetry functions. The operator can send commands and review telemetered data in the same format as during the mission. The simulator operates in real-time and is flexible enough to either simulate or fully integrate parts of the flight hardware. Such is the case for instance for the on-board computer with its complex programmable control algorithms. However, flight hardware in the loop is in no way limited to any particular unit of the flight subsystem. The simulator can also be remotely linked to the ground station and use actual commands as direct inputs for its operation. A colorgraphics driven by the simulated dynamics displays the spacecraft motions and warns the operator of eventual losses of telemetry and command capabilities during attitude anomalies. Following is a partial list of the FLIGHT SIMULATOR capabilities. S Provide an independent means to evaluate and validate a control system design; S Support the development of Control Center (hardware and software) and serve as a training facility for the control operators; S Develop and verify the spacecraft sequence of events; S Help in developing and evaluating, in real time, the on-orbit Operational and Recovery Procedures; S Maximize satellite life through maneuver optimization, and S Support the satellite mission throughout the spacecraft life, providing a test bed for flight anomaly investigation. This last point is significant since, in general, a satellite operator has no guarantee as to the availability of a spacecraft manufacturer’s facility for the full duration of a satellite mission. The COMSAT FLIGHT SIMULATOR is fully operational and is already supporting the STC/DBS (Satellite Television Corporation/Direct Broadcast Satellite) program. COMSAT concurrently developed a flight simulator for INTELSAT VI. These two simulators represent second-generation designs compared to the first real-time, hardwarein-the-loop simulator which was built for INTELSAT V.

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